紧急请教GMAT数学题

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7.51, 8.22, 7.86, 8.36, 8.09, 7.83, 8.30, 8.01, 7.73, 8.25, 7.96, 8.53

A vending machine is designed to dispence 8 ounces of coffee in to a cup. After a test that recorded the number of ounces of coffee in each of 1000 cups dispenced by vending machine, the 12 listed amounts in ounces, were selected from the data. If 1000 recorded amounts have a mean of 8.1 ounces and a standard deviation of 0.3 ounces, how many of 12 listed amounts are within 1.5 standard deviations of the mean?

A. 4

B. 6

C. 9

D. 10

E. 11

ernestnie

8.1-0.45<x<8.1+0.45  ==>7.65<x<8.55

Answer: E